docs: def get_last_next(self, date):
          """Provide the last and next leap-second events relative to a date
  
          Args:
              date (float): Date in MJD
          Return:
              tuple:
          """
          past, future = (None, None), (None, None)
  
          for mjd, value in reversed(self.data):
              if mjd <= date:
                  past = (mjd, value)
                  break
              future = (mjd, value)
  
          return past, future